The present invention relates to a system which exhausts air from the foundation of a dwelling or other building structure. More particularly, the present invention relates to a ventilator with an electrically powered fan which expels air from within the building structure to the outside environment.
A number of ventilators with automatic, temperature responsive louvers are known, including U.S. Pat. No. 4,962,882 to Sarazen, Jr. et al. A bimetallic element provides a temperature operative mechanism to open and close the shutter elements of many of these vents. A number of ventilators powered by a fan are known, including: Japanese Publication No. 55-121335A to Nobutou, Japanese Patent Publication 56-53331A to Nakamura. U.K. Patent Application GB 2 115 922A to Eccles, Brevet d'Invention No. 545,591 to Mertz, and those disclosed in the following U.S. Patents:
______________________________________ U.S. Pat. No. Inventive Entity ______________________________________ 4,829,882 Jackson 4,136,822 Felter 4,006,672 Matsuyoshi et al 3,974,754 Powlesland et al 2,510,524 Schramm ______________________________________
However, the suction capability of such powered fans diminishes significantly with distance measured from the rear edge of the fan housing. Moreover, there are often locations of the foundation crawl space that are inaccessible to the suction produced by the powered fan of such ventilators. Some of the foregoing patents disclose the use of humidity sensors and temperature sensors to control operation of the fan.